Automatic choke



May 22, 1956 R. R. Hu-rcHlsoN AUTOMATIC CHOKE Filed NOV. 12, 1953 ATTORNEY yto the thermal element by a tube.

Unite States atent l 2,746,438 AUroMAric enorm Robert R. Hutchison, Birmingham, Mich., assigner to General Motors Corporation, Detroit, Mich., a corporation of Delaware `Application November 12, 1953, Serial No. 391,555

` 6 claims. (ci. 12slieu The present invention relates to internal combustion engines and more particularly to automatic choke means for such engines. 4

To Vfacilitate the starting of a cold internal combustion engine, it is advantageous to employ an excessively rich `fuel mixture. Such a mixture is usually obtained by closing a choke valve in the carburetor. In order to eliminate the necessity for the engine operator manually actuating the choke valve, means may be provided for automatically adjusting the choke to its proper position. The most common means of accomplishing this is to employ a thermal responsive element that is operatively connected to the choke valve. During cold conditions the thermal element will close the choke valve, but as the engine warms up to its normal operating temperature the choke valve will be opened to allow the use of a e more economical fuel ratio. Since the correct setting of the coke valve is primarily a function of engine temperature rather than the air temperature, the thermal element is preferably responsive to the engine temperature. Accordingly, it is proposed to place a tube or stove in the engine exhaust system and connect the stove Thus as theexhaust gases heat up the stove, warm air will ow to the thermal element.

It is also proposed'to provide baffle means inside of the stove that will greatly increase the amount of heat transferred from the engine exhaustV gases to the air in the stove. By increasing the amount of heat in the air the elfects of the heat lost by the air when owing through the tube from the stove to the choke will be minimized.

` more clearly show the stove for the automatic choke.

Referring to the drawings in more detail, `the present invention may be embodiment in any suitable engine 10. However, inthe present instance, the invention is shown on a so-called V-type engine 10 having two aligned banks of cylinders 12 `and 14 angularly disposed in the engine block 16. A pair of heads 18 and 20 having cavities 22 formed therein are secured to the faces 24 on the sides of the engine 10 so that the cavities 22 in the heads 18 and 20 register with the openings formed by theV cylinders 12 and 14. These cavities 22 cooperate with the pistons 26 to form combustion chambers 28.

An induction system may be provided on the engine 10 for delivering a combustible charge to each of the cylinders 12 and 14. The induction system 30 includes an intake manifold 32 disposed between the cylinder heads 18 and 20 and having a carburetor 34 mounted thereon. During engine operation air will be-drawn downwardly through the carburetor 34 past the fuel jets in the venturi. This will result in the atomization of a liquid fuel which is mixed with the air to forma combustible charge. The charge will then ow pastlthe throttle valve and be discharged into the distribution passages 36 formed by walls 37. The distribution passages 36 will then direct the flow of the charge into the various cylinders 12 and 14.

An exhaust system 38 and 40 may be provided in each head 18 and 20 for removing the burned exhaust gases from the cylinders 12 and 14. Each system 38 and 40 includes a short exhaust passage 41 for each cylinder. The'passage 41 extends through the head 18 or 20 to carrythe exhaust gases from an exhaust valve seat 42 to an exhaust port 44 inthe side of the head lS or 20. An exhaust manifold 46 may be provided to collect the gases as they are discharged through the ports and the other end thereof engaging one end of a rocker arm 56. The rocker arm 56 is pivoted on the pin 58 so that outward movement of the push rod 52 will rotate the rocker arm 56 and depress the valve stem 60 and open the exhaust valve 48. When this occurs the gases may escape into the exhaust system and the associated manifold 46. A coil spring 62 concentric with the stem 68 opposes the pushV rod 52 assembly and resiliently biases the valve 48 toward the closed posinon. r

An exhaust cross-over passage 64 may beprovided through the intake manifold 32 to interconnect the two separate exhaust systems 38 and 40. This cross-over passage 64 extends through the intake manifold 32 so as to form a heating chamber 66 that is in heat exchanging relation with the walls 37 of distribution passages 36 of the induction system 30. The opposite ends 68 of the cross-over passage 64 are connected to the exhaust passages 41 by one or more short passages 70. When the engine 1t) is cold the thermostatically controlled heat valve 72 in the exhaust manifold 46is closed. This will cause the exhaust gases to back up in the manifold 46 and be diverted through the cross-over passage 64. This will heat the walls 37 of the induction passages 36.' Thus even though there is a tendency for the cold fuel particles to precipitate out of themixture onto the walls 37 of the passages 36, they will immediately be evaporated by the heat thus insuring the complete vaporizat'ion of vthe fuel mixture in the induction system. When the engine 10 warms up the heat valve 72 will be opened by thermostatic means to allow the exhaust gases to flow directly into the exhaust pipe. Therefore, during normal engine operation there will only be a periodic oscillation of gases through the cross# g over passage 64.

To provide an excessively rich fuel mixture during certain operating conditions, choke valve means 74 may be provided in the carburetor 34 anterior to the fuel jets. Thus when the choke valve is closed the fuel-air mixture will be rich'but when the valve is open, the normal economical fuel ratio will be obtained. In order to eliminate the necessity for `manually adjusting the choke when the engine 10 is cold, a thermal responsive element such as a bimetallic coil spring 75 may be prorespectively.

Since the air-fuel ratio is more dependent on the engine temperature than the air temperature, means may be provided for making the thermal element responsive to engine temperature. `This may be accomplished by heating the interiorof the housing 76 with air heated by the engine 10. In the present instance a tubular stove 78 is placed in a lhole S drilled diagonally through the intake manifold 32 so as to be disposed inside of the heating chamber 66.

.Thus the air inside of the stove 78 will be in heat exchanging relation with the hot exhaust -gases in this chamber 66.

One end 82 of the stove 7S is open to the atmosphere while the other end 84 is closed by a threaded plug 86. A tube 8S may have one end thereof .fitted into a hole 90 in the manifold 32 so as to communicate with the closed end 84 of the stove 78. The opposite end of the tube corn- Vmunicates with the interior of the housing 76 for the thermal element. Thus air may enter the open end of the Vstove and travel upward through tube 88 and into the housing 76 thus heatingthethermal element proportional to engine temperature. Convection may be relied on to induce this llow of air into the housing 76, but it is preferable that the interior lof the housing be interconnected with the induction system 3l) so that the vacuum present in the system will create a positive flow of air.

Although the air llowing through the stove 78 is in heat exchanging'relation with the exhaust gases in the heating -chamber 66, unless provision is made therefor, there will be a thin layer of stagnate air on the surface of the stove 73 which will materially `interfere with the heat transferred to the air in the stove 78.. Since the majority of the air that reaches the inside of the housing 76 travels through the center of the stove 78, it is desirable to stir or mix the air llowing through the stove 78 to insure a complete heating of the air. This may be accomplished by equipping the stove 78 with any suitable baflle 92 that will disrupt the flow-of air therethrough. In the present instance this baille 92 comprises an elongated member 94 that extends the length of the stove 7S. The member 94 is provided with a spiral iin 96 that engages the inner Walls 98 of the stove 7S. Thus as the air flows through the stove 78 it will be divided into two columns that are forced to rotate as they progress through the stove '78. This will thoroughly mix or stir the air and reduce the effects of l the boundary layer by causing all parts of the air to come in contact with the walls 98 of the stove 78 thus resulting in a more complete heating of the air. Since the heat transferred to the air is greatly increased, the effects ofthe heat losses suffered when the air ilows through the tube 83 will be greatly decreased so that the temperature in the housing 76 will be a closer reflection of the engine 10 temperature.

While the foregoing description and figures have been confined to one embodiment, it will lee-apparent to those skilled-in the art that numerous modifications may be made without departing from the spirit thereof. Accordingly, it is to be understood that the foregoing is to be considered as illustrative only and in no Way restrictive, reference being had to the appended claims to determine the scope of the invention.

What is claimed is:

1. In an engine having two aligned banks of cylinders, an induction system for delivering a combustible charge to said cylinders, a separate exhaust system for each bank of cylinders, a crossover passage interconnecting said exhaust systems, choke means disposed in said induction system for controlling the mixture of said combustible charge, a thermal responsive element on said choke means to actuatesaid choke in response to temperature changes, and a tube having a portion thereof disposed in said crossover passage in heat exchanging relation with the gases therein, and baille means disposed in said portion, one end of said tube being connected to said thermal responsive element.

2. In an engine having two banks of aligned cylinders, a fuel induction system for delivering a combustible charge of fuel to said cylinders, choke means in said induction system for varying the fuel mixture, a thermal responsive element connected to said means to actuate said choke means in response to temperature changes, a separate exhaust system for each bank of cylinders, a crossover passage interconnecting each of said exhaust systems, said crossover passage being in heat exchanging relation with a portion of said inductonsystem, a stove disposed in said crossover passage in heat exchanging relation with the exhaust gases, baffle means inside of said stove, and a tube interconnecting said stove and said thermal responsive element.

3. In an engine having two banks of aligned cylinders, a fuel induction system for delivering a combustible charge to said cylinders, choke means in said induction system for varying the fuel mixture, a thermal responsive element connected to said means to actuate said choke means in response to temperature changes, a separate exhaust system foreach bank .ofcylinders, a crossover passage interconnecting each of said exhaust systems, said crossover passage beingin heat exchanging relation with .a portion of said induction system, a tube disposed in said crossover passage in heat exchanging relation with the exhaust gases, said tube being positionedadjacent said induction system, spiral baille means in said tube, and a second tube interconnecting one end vof said first tube with said thermal element.

4. In an engine having two aligned banks of cylinders, a fuel induction system for delivering a combustible fuel mixture to said cylinders, a thermal ,responsive choke in said induction-system for varying the mixture of said fuel in response to temperature changes, a separate exhaust system for each of said banks of cylindersfor removing the hot gases from saidvcylinders, a crossover passage interconnecting said exhaust ssytems, -a heating chamber formed yin said Acrossover passage in heat exchanging relation with said induction system, a stove disposed in said chamber in heat exchanging relation with said exhaust gases, a spiral baille .disposed in said stove, and a tube interconnecting said-stove with said choke means.

5. vIn an engine having .two aligned sets of cylinders, an induction system having distribution passages for delivering a combustible air-fuel mixture to said cylinders,

said induction system including chokemeans for varying said air-fuel mixture, a separate exhaust system for exhausting the hot gases from each .bank of cylinders, a

crossover passage interconnecting said exhaust systems and forminga vheating chamber in heat-,exchanging relation vwith said distribution lpassages, a thermalresponsive element operatively connected to said choke -means for actuating saidmeans in response to temperature changes, a tube having the rst end thereof associated with said element and having the second end thereof open to the atmosphere to. allowair to flow through said tube to said element, a portion of said tube being disposed in said heating chamber in heat exchanging relation with said hot exhaustgases, and a spiral baille disposed inside of said portion of said tube, said baflle being positioned to stir the flow of air through said portion.

6. In an engine having a block with two aligned sets of cylinders therein, a pair of parallel spaced cylinder heads secured to said block, each of said heads registering with one of said sets ofcylinders, an exhaust system formed in each of said headsto exhaust the hot gasesfrom said cylindersan.intake manifold mounted on said engineand having distribution passages formed therein to communicate with said cylinders, a carburetor mounted on said manifold to discharge a combustible air-fuel mixture into said distribution passages, choke means on said carburetor adapted to vary said air-fuel mixture, a. housing on said carburetor-containing a thermal responsive element operativelyv connectedtto said choke, a crossover, passage positioned in said manifold to interconnect said exhaust systems 'and form afchamber in heat exchanging relation with said distribution passages, a stove disposed 5 inv said crossover passage adjacent said distribution passages in heat exchanging relation with said exhaust gases, one end of said stovefbeing open to the atmosphere and the othex` end thereof being operatively connected to said housing by means of a tube, andan elongated spiral baie disposed in said stove.

References Cited the Ie of this patent UNITED STATES PATENTS Meinzinger. et al. Sept. 29, 1953 

